Simon's SQL

use msdb

--select top 10 * from backupfile
--select top 10 * from backupmediaset
--select top 10 * from backupmediafamily

declare @sql nvarchar(4000)
if exists(select OBJECT_NAME(id) from syscolumns where name='compressed_backup_size') begin
	set @sql = '
	select top 1 @@servername as servername, case when sum(compressed_backup_size)convert(varchar(8),getdate()-30,112)
	group by convert(varchar(8), backup_start_date, 112)
	order by sum(backup_size) desc
	'
end else begin
	set @sql = '
	select top 1 @@servername as servername, ''N'' compressed_backup
	, convert(numeric(10,2),sum(backup_size/1024/1024/1024.0)) as [backup_size(GB)] from msdb.dbo.backupset with(nolock)
	where backup_start_date>convert(varchar(8),getdate()-30,112)
	group by convert(varchar(8), backup_start_date, 112)
	order by sum(backup_size) desc
	'
end

exec(@sql)